The present invention relates to a solid-state image pickup device, and more particularly a solid-state image pickup device of the type wherein a photosensitive or photoconductive layer is formed over a solid-state image pickup plate having circuit elements capable of charge transfer or having the X-Y addressing capability. The present invention has for its object to provide a solid-state image pickup device which may avoid blooming when the intensity of the incident light is high and which has an automatic electrically operated aperture control function.
Japanese Patent Publication No. 30768/1970 discloses the so-called X-Y addressing type solid-state image pickup device wherein a matrix of photosensors or photodiodes is combined with a field-effect transistor circuit which scans the matrix in both X and Y directions. Japanese Laid-Open Pat. Nos. 1221/1971 and 26091/1972 disclosed BBD (bucket brigade device) and CCD (charge-coupled device or charge transfer device) which are of the self-scanning type and capable of minimizing the spike noise generated together with the scanning pulses. Both the matrix of photosensors or photodiodes and the field-effect transistor circuit or an array of charge transfer elements must be formed on the same substrate so that the occupancy of the optical aperture per unit area is 1/3 to 1/5 at the most.
In order to improve the occupancy of the optical aperture, Japanese Laid-Open Pat. No. 91116/1974 teaches a solid-state image pickup device in which instead of photodiodes a photoconductive element is used as a photosensor and combined with an X-Y addressing means. Japanese Laid-Open Pat. No. 21166/1975 also discloses the combination of the above-described sensitive photoelectric element with the array of charge transfer elements. In either case, the electrode over the photosensitive or photoconductive film is maintained at the same potential as the semiconductor substrate or grounded.
In above condition, the sensitivity of the photosensitive or photoconductive film is constant in any circumstances of the incident light, so blooming occurs in high-light condition and automatic optical aperture control lenses must be used to avoid blooming, but such lenses are usually expensive and heavy.